Containers (cans) for storing, for example, coffee beans and ground coffee are recapped many times with over-caps for repeated use. Among such cans, there is known a can in which a section to be opened of a can upper lid is partitioned by an annular curled section and the inner side of the annular curled section is tightly sealed from a can lid rear surface by a gas barrier multilayer synthetic resin film including an aluminum foil layer. As a method of cutting and opening the film of the upper lid of such a can, there is known a method of cutting based on a screw configured such that a female screw is formed on the inner circumferential surface of a lower part of an over-cap and a male screw is formed on the outer circumferential surface of an upper part of a can main body, a cutter in a folded state is mounted on a top plate rear surface of the over-cap, and the over-cap is screwed into the can main body after the cutter is raised up, whereby the over-cap is displaced downward while rotating and the cutter pierces into and cuts the film in a circular shape (see, for example, Patent Document 1). In such an over-cap opener of the screw type, the cutter is mounted on the over-cap in the folded state and needs to be raised up by a fingertip when the can is opened. After being raised up once, the cutter is always in a projected state from the top plate rear surface of the over-cap. Therefore, there is a risk that a user's finger is cut when the user opens and closes and uses the over-cap.
There is also proposed open cap openers in which an opener configured by an annular cutter having an annular blade is formed separately from an over-cap and the annular cutter for cutting, in opening a film, the film in a circular shape by gripping the opener by fingers, directly piercing the annular blade into a film, and directly rotating the opener in that state and a crowned over-cap are combined (see, for example, Patent Documents 2 and 3). Among such open cap openers by the annular cutter, the open cap opener described in Patent Document 2 is an open cap opener of a type in which, after the film opening, the opener is housed on the inner side of the over-cap in a posture in which the annular blade faces the top plate rear surface of the over-cap. The open cap opener described in Patent Document 3 is an open cap opener of a type in which the opener is not housed on the inner side of the over-cap after the film cutting and, after the film is cut, the film is left in a state in which the opener is fit in the annular curled section of the can upper lid (i.e., a state in which the annular blade faces the inside of the can main body). In the open cap openers, since the annular blade is not exposed to the outside after the opening, it is possible to eliminate the risk that the finger is cut by the annular blade when the over-cap is removed from the can main body.